Cosmetic formulations have to have a number of properties in order to be suitable as nail varnishes. In this connection, it is particularly important that skin and nails are not irritated, the formulation can be applied easily, homogeneous and shiny films are formed upon application and these dry rapidly. Moreover, the film must adhere well to the nail surface, be as flexible as possible, and have good impact resistance and good wear resistance in order to prevent cracking and chipping of the nail varnish. For this, it is necessary for the cosmetic formulation to be able to form a hard but also flexible film. Also advantageous is a good resistance of the hardened film towards water in order to avoid detachment from the nail upon contact with water, for example during handwashing or washing up.
In this connection, plasticizers in nail varnish formulations improve the flexibility of the films and also influence other important parameters such as the shine, the drying time and the adhesion to the nails. For a long time, phthalates, such as dibutyl phthalate or camphor, or polymeric condensation products of formaldehyde or other aldehydes have been used virtually exclusively as plasticizers in nail varnish formulations. However, since these substances have proven to be injurious to health, there is a desire to replace these in nail varnish formulations.
U.S. Pat. No. 5,227,155 mentions for the first time the use of acetyl tributyl citrate (ATC) as plasticizer in nail varnish formulations. This substance has nowadays already to a large extent replaced the aforementioned health-injurious plasticizers. However, ATC leads to considerably reduced shine compared to the plasticizers used previously. Moreover, on account of its low molecular mass, ATC has a tendency to migrate out of the nail varnish film and deposit itself on the surface of the film. As a result, the surface of the film looks dull and the plasticizer effect in the nail varnish itself is lost. Moreover, nail varnish formulations with ATC as plasticizer harden only slowly.
WO 03/094870 A mentions, inter alia, propylene carbonate as a potential plasticizer for nail varnish formulations. However, propylene carbonate in nail varnish formulations exhibits a significantly too slight plasticizer effect in order to be able to be used constructively and efficiently. Moreover, propylene carbonate is volatile and can migrate out of the nail varnish film.
US 2010/0158835 A1 describes specific low molecular weight carbonates, such as, for example, glycerol carbonate, as plasticizers for nail varnish formulations. However, it is known for these plasticizers that the hardened nail varnish has poor resistance towards water. This is evident from a swelling or disintegration of the nail varnish and a reduced adhesion of the nail varnish on the nail. Moreover, nail varnish formulations with glycerol carbonate as plasticizer harden somewhat too slowly.
There was therefore a need for nail varnish compositions which comprise plasticizers which do not exhibit toxicologically unacceptable properties, are nonvolatile and, moreover, have only a slight ability to migrate from the film or through tissue and skin. Moreover, the nail varnish compositions should harden rapidly and have good water resistance.